In recent years, it has generally been accepted that ceiling lighting fixtures should, at their light projecting ends, coincide flushly with the plane of the ceiling in which the lighting fixture is installed. From a safety standpoint, unless the lighting fixture is of the elongated panel type, a circular aperture is cut or otherwise provided in the ceiling and a rigid, usually metallic cylindrical housing is pushed upwardly through the aperture and secured in some manner by a lateral support means to joists or beams supporting the ceiling. Within this housing, a lamp socket for an incandescent bulb is ordinarily provided which socket may be connected by BX cable or other wiring through the wall of the housing to the edifice lighting circuit. In some cases, a lamp socket may be loosely disposed in the upper part of the housing to receive an incandescent light bulb inserted through a reflector disposed in the lower part of the housing. In other cases, some type of metallic bridge has been secured across the inside of the upper part of the housing where the socket may be fixedly or pivotally mounted.
In recent years it has become desirable to replace such standard incandescent bulbs with compact florescent lamps. By such replacements, less energy is required and the lighted fixtures dispense substantially less heat. However, replacing incandescent bulbs which screw into a conventional socket disposed loosely or fixedly within a housing, is not a simple matter since a florescent lamp requires a special plug-in socket different from the threaded socket for an incandescent lamp, and a transformer. These must be properly supported and cannot be left to dangle within the housing. Additionally, for the most effective heating, the elongated florescent lamp or lamps should be disposed close to the axis of the housing and its reflector.
Thus, retrofitting recessed incandescent lamp fixtures with florescent lamps has presented such problems that it has been considered simpler to remove the entire housing and rebuild the inside of the fixture to install what is needed for a florescent lamp replacement of an incandescent lamp fixture.